Arrangements for removing moisture from enclosures are widely used in industries in which products stored must be maintained at a sufficiently low moisture level or content to preserve their functional integrity. The ability to maintain reduced moisture levels is particularly critical in laboratory environments since it is commonly required to store chemicals, materials, and products which are particularly susceptible to moisture damage. Vacuum desiccant devices capable of producing and maintaining a vacuum within the respective working chambers are known in the art.
It is also well known that desiccation is limited by the maximum safe working pressure the device can withstand. While a plethora of such devices are known in the art of various designs and configurations, many of them are of less than ideal construction. The ability of a vessel to maintain structural integrity is limited by the rupture strength of the valve and pipe systems and the tensile strength of the walls. This point is usually the point at which there is the lowest tensile strength which limits the usefulness of the entire structure. As the pressure inside the desiccator decreases, the likelihood of rupture increases.
Prior art vessels are severely limited in strength as size increases and are problematic to scale up. A sphere, in contrast to all other configurations, is perfectly symmetrical and has an equal distance from the center point to any point on the surface. The true sphere has the smallest surface area among all surfaces enclosing a given volume and it encloses the largest volume among all closed surfaces with a given surface area.
While semi-spherical hollow desiccators exist, to the best knowledge of the inventors, no true hollow, spherical desiccators are known in the art. In this respect, the spherical vacuum desiccator device of the present invention substantially departs from conventional concepts and designs of the prior art. By providing a desiccator with a true spherical working or desiccation chamber, it is possible to achieve substantial safety of the device. Any other shape provides weak points at the joints and corners which forces the user not to apply extreme pressure or risk breakage or injury.
In the prior art, glue, solder, epoxy, and other binding agents as well as welding, etc. are often required to secure the structural elements of the desiccator together. For example, in the formation of desiccator cabinets and the like, the connecting area between one side and another must be sealed. In a typical box-like structure, there are many engagement areas providing multiple points of weakness, thus making a strong seal difficult. These connecting areas are prone to leakage and may become one of the weakest areas in the device, especially when the body of the desiccator and the interior region thereof are exposed to substantial positive and/or negative pressure conditions. The need to fortify these connecting points and the use of multitude structural elements increases the cost and complexity of such prior art desiccation devices.
It is known in the art, such as is disclosed in U.S. Pat. No. 5,807,422 to Grgich, et al, that the lower the velocity of the gas, the closer the dynamic capacity is to the static capacity of the desiccant. As velocity is decreased, the capacity of the desiccant, namely, the ability to absorb liquid from a gas, is increased because the time that the gas is in contact with the absorbent is increased. As the linear gas velocity through the desiccant bed is lowered, the dynamic capacity of the desiccant is increased since the gas molecules are in contact with the absorbent for a greater period of time. Slowing the velocity of the gas may be accomplished by increasing the size of the vessel or decreasing the pressure inside the vessel. This may be accomplished by decreasing the temperature. However, the Grgich device is limited in structure because a true sphere is not disclosed. Further, a hollow area for equal air flow is not disclosed, but rather a spherical desiccant absorption unit composed of zones and so does not solve the present problem of equal air flow and unlimited scalability while maintaining complete structural integrity. While temperature control is also an issue in the Grgich patent due to the limited volume in the absorption bed, this problem has been solved by the present invention by providing a single air cavity structurally designed for equal air flow.
Thus, there has been a long felt and unsolved need for a simple, inexpensive, and reliable desiccator capable of withstanding great positive and negative pressure, the desiccator capable of providing a uniform distribution of gas within the working chamber.